In studies assessing the performance of crops in response to green manure generally are not considered the effect of roots. However, such effects may contribute to increase the scientific understanding towards this technique. The effect of the root and of the aboveground part of two legume species, Crotalaria juncea and Canavalia ensiformis, were evaluated on cabbage yield in two crops. The experiment was arranged in randomized blocks with 4 replications in a factorial design (2 x 3) + 2 (2 legumes species - Crotalaria juncea (sunnhemp) and Canavalia ensiformis (jack beans), 3 plant parts (root, aboveground part and the whole plant) and 2 additional treatments (mineral fertilizer 100% and 50% of recommended N). The green manure was applied to the surface. The cultivation with the aboveground part or the whole plant of sunnhemp or jack beans reduced the necessity of fertilization with mineral N in 50%, but the cabbage yield was reduced with the cultivation with the root system of jack beans. Areas with the aboveground part or the whole plant of sunnhemp or jack beans presented higher residual effects on the second crop with mineral N fertilizer. The cultivation with the roots of these legumes resulted in no residual effect different from mineral fertilizer with 50 or 100% of recommended N.